Improvement in sliding- calipers



A. E. WHITMORE.

Registering Calipers. l

Y Patented J`u|y'27,. i869.

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ANDREW E. WHITMORE, or BOSTON, MASSACHUSETTS.

mmm Patent No. 93,026, dated .my 27, 1869.

IMPROVEMENT IN SLIDING- CALIPERS.

The Schedule referred to in` these Letters Patent and making part o fthe same.

To all to 'whom these presents sliallcome.-

Be it known that I, ANDREW E. WHITMORE, of Boston, in the county ofSuffolk, and Commonwealth of Massachusetts, have made an invention ot'anorigiual and useful instrument for determining the thickness ofsheetmetals, diameters of cylinders, dto., which may be termedSelf-Regulating Calipers; and do hereby declare the following to be afull, Iclear, and exact description thereof, due reference being had tothe accompanying drawings, making part of this speciiication, and inwhich- Figure l is a plan,

Figure 2 is a side elevation,

Figure 3, an end elevation,

Figure 4, a vertical and longitudinal section, and

Figure v5, a transverse section of an instrument embodying myinvention.v

The invention herein tov be described relates to a stationary and amovable jaw, mounted upon a tubular shank or bar, enclosing a malescrew, which passes through and so actuates the movable jaw as toproduce sliding movements of it upon the shank, toward and away from thestationary jaw, which is iixed to the shank, the said shank, at itsopposite end, being provided with a fixed-'disk or collar, upon which isengraved a scale for determining vthe infinitesimal fraction of an inchwhich is measured by the instrument, an adjustable index-pointer Abeingapplied to the adjacent extremity of the screw, and in conjunction withthe scale before mentioned, in such manner as t0 be readily loosenedupon the screw and returned to the normal or zero-point of the scale,should any disarrangement or discrepancy manifest itself after movingthe adjusting-nut of the movable jaw upon the screw which actuates it,the whole being as hereinafter explained.

In the drawings, to whighallnsion has before been made Aas accompanyingthis speciiication, and which illustrate my inventiona denotes anattenuated tubular bar,'having affixed upon one extremity, and at rightangles to its general axis, a stationary jaw, l).

Within the bore of the barra, (which maybe square or.polygonal,) andturning in suitable bearings formed in each end thereof', I dispose along male screw, c, the extremity of this screw farthest-'from the xedjaw of the instrument, having applied to it a thimble,

d, such thimble in turn being provided with an indexpointer, e,projecting from its front face, at right .angles to its bore, andimpinging against the rear face of a dial-plate, j; affixed to or makingpart of the contiguous-end of the bara, the said cuter face'of thedialp'late having engraved upon it a .scale to .denote the fractions ofan inch, the divisions of such scale varying in-'number with the degreeof exactitudewhich it i as of like size and shape with its fellow-jaw,and slid-v ing easily upon thev bar a,.a sectional nut, h, beingswivelled within its upper part in-v such manner as to be depressed intoengagement withthe screw c, or elevated from contact therewith. r

Each extremity of the screw c should be provided with a milled head, i,for rotating it.

The above comprises the constituent parts and mcchanical construction ofan instrument'- embodying my invention, its action being as follows:`

For measuring large bodies, when great accuracy is not essential, themovable jaw may be used in connection only with the scale upon theside'of the bar a.-

The adoption of the adjustable sectional nut is to allow ofrapid'changesof the movable jaw, toward or away from the stationary jaw,in order to adapt the instrument to great variations in distancesmeasured by it.

The employment of the sectional nut, as described,

eiects an economy in the wear upon the screw', and

in the time required to use the instrument.

The exactness of measurement of which the instrument is capable,is, ofcourse, directly dependent upon the number of threads of the screw to'an inch, and of the number of the divisions of the scale upon thedial-plate at the end of the bar a.

In the present instance, the. screw is cut with twenty-live threads tothe inch, and thel circular scale is,

vdivided into forty points; hence, a partial turn of the screw,suiicient to move the indicator-point the distance of one division uponthe scale, will produce a sympathetic movement of the movable jaw uponthe bar q to the extent ofone-thousandth part of an inch, this numberbeing the multiple of the number of threads to the inch of the screw,and of the subdivisions of the scale.

It will probably never be found, in practice, necessary to exceed theabove fractions of an inch.

The object in applying thesleeve d to the screw c, in an adjustablemanner, is to -7enable the index-pointver to be set at the zero. of itsscale, when the movable jaw coincides exactly with the scale upon theside ofthe bara, or when the two jaws are in contact with each other.

The adoption of the sectional nut, as before Vobserved,'allows of rapidand extended movements of the movable jaw, which would otherwise requiremuch time to eiiect, were the screw alone employed for this purpose.

By encasing the screw within the bar of the instrument, it is protectedfrom injury, which would inevi.

tably result to it but for this or some analogous protection.

I would remark that I have contemplated applying the intermediate jawitothe bar in such manner as to be able tosecure it thereto in anadjustable manner, independent of the screw, and to adapt the screw toproduce movements of the outer jaw for giving the 'small fractionalparts ofthe measurements.

By this mode, the threads of the screw need only be cut upon a smallportion of the length of the rod of which it is composed, vand theindex-pointer may be more readily adjusted.

